1. Field of the Invention
The present invention relates to an image processing apparatus and image processing method and, more particularly, to an image processing apparatus and image processing method for generating an image using ray tracing.
2. Description of the Related Art
Recently, computer graphics (CG) have been used in various fields. CG is widely used even in the design field. In this field, a technique for generating an image that is more faithful to a real object is required.
As a method for faithfully reproducing a real object using CG, various techniques including the following ones have been known. Examples are a method using a multi-angle spectral reflection property to simulate reflection by a paint or the like having optically complicated properties, and a method using the multi-angle spectral reflection property of an object to reproduce a highly realistic image on the monitor. Other examples are a method using a spectral refraction property to reproduce the color of reflection, and a method using multiband data captured by a multispectral camera.
Image generation methods in CG include a scan line method, Z-buffer method, and ray tracing method. Of these methods, the ray tracing method is suitable for generating an image faithful to a real object because it can express reflection and refraction by tracing the propagation path of light in a 3D space. However, the ray tracing method needs to repetitively trace the paths of a great number of rays. To obtain a high-quality image in a complicated scene, this method requires an enormous amount of calculation. As efficient algorithms for the ray tracing method, binary space partitioning, bounding volume, and the like are proposed. For example, as a technique using binary space partitioning, there is proposed a method of partitioning in advance a virtual space into a plurality of voxels, performing crossing detection for only objects in voxels through which rays pass, and generating an image.
However, the conventional methods of generating a CG image do not consider the light distribution characteristics of light sources. These methods cannot reproduce a change of a shadow which is generated in a scene depending on light sources having different light distribution characteristics such as a fluorescent light and light-emitting diode (LED) illumination.
A general ray tracing method handles light as wavelength-independent uniform rays. This method cannot accurately reproduce a physical phenomenon in which the behavior changes depending on the wavelength, such as refraction of light passing through an object.